"Amazon seems to have seriously cutting edge infrastructure"
How do you know? Based on what they sell through AWS? This is not super evident - they might have duct taped bunch of shitty stuff and rely on people on-call 24x7 to keep system running.
There's only so much duct-tape you can throw at a problem before it becomes unmanageable. The scale, complexity and reliability of AWS indicates that they are indeed running a tight (and tidy) ship.
Yes, seriously legacy software (still a lot of Perl in their production web code, including ancient Perl template engines) and the on-calls are truly bad. AWS is more modern, but still not entirely awesome from what I've heard.
On the plus side, hiring people out of there after a year is usually pretty easy.
